Is my external efi fuel pump causing vapor lock?

[Biggredd2069]

Have a fitech efi on my 68 Newport. Been a problem for years since day 1 but so many other projects and life things that take priority in finally done with and able to focus on this. Car will start great. Run great. Then I'll park and go to start it and just cranks and cranks but doesn't start. It's the most frustrating thing ever. I do get an occasional stall and recovery with a bit of a backfire but that's small. Would an in tank fuel pump be an obvious upgrade or is there something more? I've gone down the rabbit hole wasting money and i don't trust a single mechanic anywhere anymore. I'm ready to blow this car up.

 

[Davea Lux]

1.) Check the fuel line coming to the fitech. You should get a lot of fuel with the line placed in the bottle and the key on. If it is not pumping, you either have a bad connection someplace or the pump is defective.
2.) If the fuel system appears to be working, pull the coil wire from the distributor and place it about 3/16" from the block. You should get a good arc from the wire to the block when cranking. (Do these tests when you are having trouble starting the car)
3.) Electrical components do not like heat. Did you convert to electronic ignition as part of the fitech upgrade? If so, check the coil, ignition control unit and the magnetic pickup in the distributor. Everything needs good connections and good grounds to function properly. Some of the early fitech units were prone to shorting out if the key was left on for and extended period.

Dave

 

[Biggredd2069]

I did replace the fuel pump last year. Feel like I've had this same problem with 2 different pumps. I did buy a pertronix distributor and coil and i did set up the wiring so it wouldn't short if left on too long. I suppose it doesn't hurt to test the pump again and the spark but I'm pretty confident those are solid. There is a gauge on the top of the pump that seems to read ok. Just seems like a heat issue but hard to know what to fix and where. I have the fuel pump by the horn.

 

[Davea Lux]

I did replace the fuel pump last year. Feel like I've had this same problem with 2 different pumps. I did buy a pertronix distributor and coil and i did set up the wiring so it wouldn't short if left on too long. I suppose it doesn't hurt to test the pump again and the spark but I'm pretty confident those are solid. There is a gauge on the top of the pump that seems to read ok. Just seems like a heat issue but hard to know what to fix and where. I have the fuel pump by the horn.

Where is your pump mounted and what are the pressure settings?

Dave

 

[Boydsdodge]

Fitech has, should have an external fuel reservoir up front after your mechanical pump. The reservoir looks like the 70s charcoal considers mounted to from rad support, it has a high pressure pump to keep the fuel inspection fully primed and with pressure. I am sure you can not run fuel injection with a regular mechanical pump.

 

[MONC440]

I have the fuel pump by the horn.

Do you mean the horn for the car under the hood? I was thinking of a in tank pump for my car and would be the best way to go as it keeps the pump cooler and quieter. I didn't have the cash for it at the the time so I placed my pump as close to the tank as possible. They do not pull fuel very well because they are made to push fuel. There is a reason all the OEM's went to in tank pumps, it sure wasn't for easy service. Do you hear the pump run for just a couple seconds when you turn the key to run without cranking it? If so the next time try turning the key on, then off, a couple of times then crank it. That should make sure you have enough pressure before cranking.

 

[CBODY67]

In the early OEM efi days, we had customers who put 100 gallon L-tank aux fuel tanks on their pickups for long distance trailer pulling (think horse trailers, cross-country). With their normal pumps, pre-efi, no problems. With EFI, could not do. Tried the biggest Holley race pumps and still no workie. That was the first time we realized that EFI took PRESSURE and VOLUME at the same time! We ended up having to get the little inline EFI pumps at about $100USD in the later 1980s. YIKES, but they worked. An area aux fuel tank manufacturer had them.

It's ONE thing to mount the reservoir/sump/pump combination on the core support by the horn as the normal pump supplies it. Then the internal high-pressure pump takes over and feeds the EFI unit. BUT to have an EFI pump mounted at that level also means "no head" (as in fuel normally at that level), so harder to pull fuel it was not really designed to pull. One reason the electric fuel pumps are always mounted much lower in the body! They get natural fuel feed.

The OTHER thing is that with that higher mounting level, it can make the integrity of the fuel line behind the pump much more critical. ALL of the fuel line sections, not just the ones visibly seen. Especially with ethanol'd fuels.

In the later 1990s, we started to experience normal wear-out of OEM EFI in-tank pump modules. The defining symptom was "extended crank time". With a fuel pressure gauge installed, the engien would crank normally until the fuel pressure hit the magic min-pressure number of about 56psi. Just as the needle touched that number, the engine fired and ran. The old manual RoosaMaster diesel injection pumps were the same way.

Just some thoughts and observations,
CBODY67

 

[SPF Required]

Hello @Biggredd2069

I have a FiTech on my ‘68 300 and had the same problems as you. My first solution was to pop the hood every time I parked it to let the engine bay air out. That was not a long term solution, but did the job for a while. after months of frustration a guy at a cars and coffee said it was probably the CPU in the throttle body getting too hot when the car is parked because it was soaking the heat up from the block and ‘fooling’ the system thinking it is overheated. He suggested replacing the aluminum spacer under the throttle body with a phenolic one. Did that and viola, the issue never repeated itself.

 

[furious70]

Where is the pump?
I've been running a walbro 255 since 2009 on the frame rail near the tank